Carburetor



Feb. 2, 1932. H, KI BY 1,843,644

CARBURETOR Filed June 18 1928 51/557 Ur flaw/es v i v 5 s Patented Feb. 2, 1932 ATENT FFIGE CHARLES H. KIRBY, OF FLINT, MIGHIGAN, ASSIGNOB TO MARVEL CARBURETER COM- PANY, A CORPORATION OF ILLINOIS CARBURETOB Application filed June 18, 1928.

This invention relates to carburetors for internal combustion engines and has as an object the provision of a non-positive r hydraulic check valve in the supply passage leading to an accelerating pump.

Heretofore it has been customary and necessary, when accelerating pumps are provided, to utilize some form of positive check or non-return valve in the fuel feeding passage communicating from the float chamber to the accelerating pump in order that on the delivery stroke of the pump fuel will be discharged through a nozzle rather than returned to the float bowl. When the accelerating'pump is operated by either a positive connection to the throttle or by means of a Connection to the air valve, the pump is operated to inject extra fuel every time the throttle is opened or the air valve opens. The extra fuel supplied by the accelerating pump is desirable only upon sudden opening of the throttle or air valve, a gradual opening thereof not requiring additional accelerating fuel because the normal fuel supply means is ade.

quate to supply metered fuel in proportion to the air supply. It will thus be seen that'a positive check valve results in the supplying of additional 'fuel at times when it is not necessary and is in fact undesirable because of the oVer-richening effect. It is therefore an object of this invention to provide a fuel passage leading to the accelerating pump so shaped that it will permit the flow of fuel towards the pump while setting up eddy currents and resistance to a rapid return flow of fuel whereby if the pump is operated rapidly, a pressure diiferential will be set up suiticient to cause a delivery of accelerating fuel substantially in accord with the requirements as to extra fuel which requirements vary in amounts according to the desired rapidity of pickup.

Uther and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawings.

This invention in a preferred form) is illustrated in the drawings and hereinafter 0 more fully described.

@n the drawings:

Serial N0. 286,187.

Figure 1 is a partly sectional elevation of a carburetor embodying the features of this invention.

Figure 2 is an enlarged fragmentary section showing the hydraulic check valve of this invention.

As shown on the drawings:

The carburetor chosen to illustrate the invention is of the type wherein an automatic air. valve controls the admission of fuel to a mixing chamber 10. In order to simplify the showing, no air inlet chamber as such is shown, the incoming air entering between ties or struts 11 below an air valve seat ring 12. An automatic air valve 13 initially seats on the ring 12 and has a central fuel discharge nozzle 14 with surrounding primary air passages 15. A. metering pin 16 restricts the fuel passagelGa to the nozzle 14, this pin being mounted in a rack 17 operated by a pinion 18 in a bottom closure 19 for an accelerating pump chamber 20.

The mixing chamber terminates in a flange 21 for attachment to the inlet manifold of an engine, the outlet passage 22 being threaded adjacent a butterfly throttle 23 to assist in breaking up unvaporized fuel flowing around the edges of the partly closed throttle.

The operation of the air valve involves cooperating with the metering pin to regulate the normal fuel supply to the engine. Abnormal demands, such as sudden acceleration, wherein the normal fuel supply lags behind the air supply due to a sudden opening of the air valve, are met byan accelerating 85 pump comprising a piston 24 connected to the air valve and moving in the chamber 20, which piston acts both as a pump to acceler ate fuel flow and as a dash pot to retard the opening of the air valve.

In the illustrated embodiment of the invention the float chamber 25 is in open communication with the chamber 20 below the piston by means of a downwardly slanting passage 26 to a saw cut 2? in the wall of the chamber 95 '20. As illustrated in Figure ltbis arrangeabove the piston is supplied through a plug 28 located near the fuel level in the float chamber, so that this and fuel supply vent.

The plug 28 is formed as a hydraulic check or one way valve by forming a passage 36 therethrough having a tapered injector nozzle form, with the end of the passage opening into the chamber 20 as a projecting nozzle 37 by cutting back the end of the plug around plug serves as an air the nozzle as indicated at 38. This form of I nozzle passage has slight resistance to flow into the chamber when the piston is moving downwardly, but sets up relatively great resistance to a return flow of fuel to the float chamber when the piston moves upwardly, this resistance increasing greatly with an increase in the speed of piston movement because of the projecting nozzle structure. Due

1 to the resistance so set up a differential pressure is set up in the chamber 20 above the piston so that fuel is forced out through apertures 40 into a central fuel passage 41 leading to the fuel passage 16a into which the metering pin projects. Similar apertures 41 near the upper end of the chamber 20 serve as air escape vents.

Y The operation of the plug 28 is thus dependent upon a rapid movement of the piston and the fuel delivered by the accelerating pump is varied in amount and is substantially proportional to the rapidity of movement of the'piston and air valve. At slow rates of opening substantially no extra fuel will be delivered to the nozzle due to the pumping made, and numerous details of construction v may be varied through a Wide range without departing from the principles of this invention, and I therefore do not purpose limiting the patent granted hereon, otherwise than necessitated by the prior art, ll claim as my invention:

In a carburetor, the combination with a mixing chamber and an automatic valve controlling the air inlet thereto and having a fuel passage there-in, of a dash pot and a chamber therefor for retarding the the opening movement of said valve, a fuel supply passage leadin to the retarding end ofthe dash pot cham er, and a plug positioned in said fuel supply passage and having a nozzle-like aperture therein so formed as to set up an increasing hydraulic resistance in proportion to the rapidity of a reeaaeaa turn flow of fuel through said aperture, whereby to eject varying supplemental quantities of fuel through the fuel passage in the air valve upon opening movements thereof.

In testimony whereof I have hereunto subscribed my name at Flint, Genesee County,

Michigan.

CHARLES H. KIRB'Y. 

